Agreed. I am considering relicensing all of my permissively licensed code because of this. The fundamental assumptions I had when releasing that code under a permissive license have been violated.
Under GitHub's legal theory (fair use), nothing you put in that license file can stop them from doing so legally.
If copyright applies, they're already in violation by failing to attribute your MIT contributions and could theoretically be sued for infringement (as they did not abide by the terms of the license).
When you use a permissive license, it’s best you stop thinking of it as your code. You’ve set it free for everyone, and while you may retain copyright in some abstract sense, it really no longer belongs to you.
While I agree with you--in that the vast majority of people who publish code under permissive licenses actually have an implied set of "moral code" restrictions that they end up surprised people violate even though they specifically allowed such by their choice of license (implying they should have chosen a different, and likely more restrictive, license)--even permissive licenses tend to at least include "you can't take my code without crediting me for taking my code", and so I can appreciate someone being upset about that not happening.
